Mike and all, It seems like with a 20 foot mast you have plenty of room to
mount everything on the mast. Mount the tribander on the bottom, mount the pair
of 2M Yagis with the proper spacing above that. The bottom 2M beam won't affect
the tribander at all and the tribander, since it has very little aperture at
144, won't affect the 2M beam much either, especially if you can keep the 2
several feet apart which you can. (The stacking distance of the 2m12 is 11ft
both in the E and H plane, so PLENTY of room). Then put 432 and 222 in
between, spaced as best you can. Or put the top 2M Yagi on the very top of the
mast, put one of the others in between the two 2M Yagis and put the remaining
Yagi between the tribander and bottom 2M Yagi. There is a common misconception
that VHF Yagis for different bands need to be spaced a distance of half the
aperture of one plus half the aperture of the other so they don't interact.
what is missed in this argument is that it assumes , say, that the 222 Ya
gi has the same aperture at 432 that it does at 222. Not true. Here's an
interesting read from the "still up and still relevant" website of the late
(RIP good buddy!) Bill Seabreeze, W3IY, who did a lot of experimenting with
stacking rover Yagis close together on the same mast (a necessity most often
for rovers). Antenna Application Note 47899
(w1rt.us)<http://www.w1rt.us/w3iy/fstack.htm> Bill stacked his 6 ft rover
yagis a foot apart and had very little interaction. You can back up from this
app note to see Bill's whole page it's an amazing piece of work.
I hate using H-frames or other stacking arrangements that go horizontally when
I don't have to, because they drastically increase wind loading and make
repairs more difficult. With a 20 foot mast you have tons of room for these 5
antennas, so don't make it more complicated than it needs to be!
(my $.02) - bill, k1DY
________________________________
From: VHFcontesting <vhfcontesting-bounces+callbill=hotmail.com@contesting.com>
on behalf of k9mk@flash.net <k9mk@flash.net>
Sent: Saturday, March 4, 2023 11:02 PM
To: vhfcontesting@contesting.com <vhfcontesting@contesting.com>
Subject: [VHFcontesting] Restacking the VHF antenna
Greetings,
At the old QTH my VHF antennas ran up the mast like most conventional
VHF antenna installs. Here at the new QTH, I wanted to increase the number
of antennas on the same 20' mast. I was considering concentrating the vhf
stacking configuration to make room for 20-10m HF antenna. My thoughts are
to mount pairs of VHF Yagi's at each end of an 8' fiberglass cross boom.
Mounting a 2M12 paired (side by side) with 222-5WL. Likewise, a second
cross boom above it with a second 2M12 with a 432-9WL on each end. Does
anyone have experience with this or a similar configuration? I would be
interested in hearing from you on your success and/or learnings.
Thanks
73 Mike K9MK
EM12JI
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